Electronic printed circuits board (PCB) and flexible printed circuits (FPC) are known. High component density is available through the use of fine line lithography and multi-layer PCB. Generally, the cost of manufacturing lithography based PCB's is substantial. However, there are applications in which high component density is not desired, but the cost of manufacturing the FPC is critical to the commercial success of the product. In some applications, the size of the FPC is determined by the shape of the product and not by the area needed to position the few electronic components. Examples for such products are toys, electronic books and other consumer products. Cheap flexible circuits may be used, among other uses, in alarm systems for card holders as is described in U.S. Pat. No. 5,373,283 and U.S. Pat. No. 4,652,865, and in electronic books disclosed in U.S. Pat. No. 6,041,215.
Various inventions concerning electronic books are cited in U.S. Pat. No. 6,041,215 disclosed by Maddrell et al. A reader may use an electronic book and is able to select an answer, for example out of a possible choice of four answers to a question in the text, by depressing a switch. The response of the user is relayed from the switch by electrically conductive leads to an electronic module, which operates a feedback unit, such as a loudspeaker, to emit a feedback signal to the user in response to a correct answer. Usually, the electronic module includes a processor, a feedback device, and a battery for power.
Most often, production of such a consumer electronic product demands intricate manufacturing techniques for inserting components in between the thickness of a sheet, the removal of special cutouts, the addition of spacers and unusual bookbinding methods. Therefore, the cost of these devices may be high due to the cost of the added electric and electronic components and to the increased costs of the manufacturing techniques employed.
To make these devices more available, it would be advantageous to reduce the cost by saving on the components and on the sophisticated printing and processing methods.
In the production of PCB and FPC it is often necessary to have an electrical connection bridging conductive lines on opposite sides of the printed circuit. The art of rigid printed circuit production has advanced to the point of making multi-layered board with highly dense and elaborate connection between layers. In simple form, as depicted in FIG. 1, a method is depicted in accordance with the prior art of creating via connection 10 between a first conductive line 12A and a second conductive line 12B on opposite sides of a rigid non-conductive board 14. The method may include drilling a via hole 10 in a location where the two conductive lines 12A and 12B overlap, and plating the drilled hole with a conductive material 16. This method may not suitable for some production of low cost FPC.
Another method in the prior art for creating via connection between conductive lines on opposite sides of thin flexible sheet is depicted in prior art FIG. 2. This method may include providing a thin flexible non-conductive sheet 20 with a first conductive line 22 and a second conductive line 24 printed on first and second surfaces, and inserting a rivet 26 made of conductive material to create an electrical connection between the line 22 and line 24 on opposite sides of the sheet 20. This method may suffer from several disadvantages: Reliability of the connection is low as the rivets may tear the thin sheet if too tight or create intermittent electrical connection if too loose; long term durability is low, specifically when the mechanical strength of the thin sheet is poor; and the rivet gives extra bulk to the circuit.